The present invention relates to a method of stopping leakage of water in a concrete structure and, more particularly, to a water leakage stopping method wherein all cracks in a leaking part of a concrete structure are caulked and hermetically sealed with a foamed hydrophilic one component type polyurethane prepolymer by means of foaming pressure and volume expansion caused by a reaction taking place between a hydrophilic one component type polyurethane prepolymer and water leaking in the concrete structure.
It is well known that a moisture-curing polyurethane prepolymer reacts with water to cure and it produces carbon dioxide gas in the course of the chemical reaction and thus foams and expands in volume, and it is said that the foaming pressure reaches 50 kg/cm.sup.2 or more in a restrained state. It is conventional practice to adopt a water leakage stopping method utilizing the properties of such moisture-curing polyurethane prepolymer, wherein an impregnating agent consisting essentially of the above-described prepolymer is injected under high pressure into a cracked part of a rock bed or into a leaking part of a concrete structure and reacted with water so as to set quickly, thereby filling the crack or gap in the rock bed or the concrete structure with the cured polyurethane foam, and thus stopping leakage of water.
The above-described conventional method, however, simply utilizes the properties of the polyurethane prepolymer that it sets through reaction with water, and intends to stop leakage of water by means of a cured nonwater permeable urethane resin formed on the surface of a leaking part of a concrete structure by applying a large amount of polyurethane prepolymer to the surface of the leaking part. Accordingly, the conventional method does not aim at caulking minute cracks in a concrete structre or restoring the physical strength and watertightness of the concrete structure itself which have been deteriorated by the leakage of water. In other words, the conventional method expects quick stoppage of leakage by the formation of the cured resin; therefore, it is general practice to mix the impregnating agent with a catalyst for accelerating the reaction of polyurethane prepolymer with water or a foaming accelerator for ensuring and accelerating foaming.
For this reason, with the conventional method, a cured urethane resin is rapidly formed on the surface of the concrete structure, while fine cracks which extend to the inside of the concrete structure are left as they are.
More specifically, the above-described conventional method of stopping leakage of water suffers from the following problems:
1. Since the surface of a leaking part of a concrete structure allows application of an infinite amount of impregnating agent, it is uneconomically necessary to consume a large amount of impregnating agent.
2. Application of the impregnating agent to the whole surface of the leaking part of the concrete structure involves difficulties in determining and confirming a necessary amount of impregnating agent.
3. If leaking water flows rapidly, the impregnating agent may be washed away, so that it may be impossible to form a cured resin in order to stop leakage of water.
4. Any excessive foaming caused by the added foaming accelerator results in moisture being lost, and this leads to a reduction in volume of the cured resin, thus failing to obtain leakage stopping effectiveness.
5. Since the cured resin is rapidly formed only on the surface of the concrete structure, cracks which are present inside the leaking part cannot be sealed hermetically but left uncaulked.
6. It is impossible to restore the deteriorated strength and watertightness of the concrete structure itself.